LONDON (AFP) - It was cramped, gloomy, the air was thick with cigar smoke and outside, bombs were raining on London. But in their underground bunker, unsung heroes were working tirelessly helping Churchills war Cabinet. Until the end of World War II in 1945, British prime minister Winston Churchill and his closest aides and ministers plotted the downfall of Nazi Germany in the labyrinth basement of what is now the Treasury. And alongside them, a secret army of backroom staff typists, secretaries, messengers slept and toiled without seeing daylight in the muggy warren of brick-walled rooms, facilitating world-changing decisions that shaped the war. I dont know quite how we did it, said Joy Hunter, a shorthand typist and personal assistant in the bunker. A teenager when she first walked down into the Cabinet War Rooms, Hunter was involved in typing up the battle orders for D-Day, the Allied invasion of Normandy. The whole thing about working underground, its very strange, really, because not only do you never see daylight but you also never have fresh air. I wont say it was very pleasant, the 84-year-old said. There were moments of extreme claustrophobia, but when you were very busy you had to keep going. The statesman at the heart of it all, Churchill, made many famous broadcasts from within the war rooms and his presence loomed large. When Churchill was around, you knew he was there from the cigar smoke, Hunter said. Telephone operator Joan Mynott recalled the wartime titan as a wonderful man. He was always, with all his staff, very dignified and always had a lot of jokes, the 89-year-old said. We were being very heavily bombed and he used to go right onto the roof. His staff went crazy. 'Im going up to watch the fireworks and he did. The Cabinet War Rooms, where so many major decisions were planned, were largely left untouched after the war. They opened to the public in 1984. The basement complex is staging a year-long exhibition, Undercover: Life in Churchills Bunker, dedicated to the people who spent the war secretly working alongside Britains leaders. It opened on Thursday, 70 years to the day since the rooms were used for the first time. Returning to the bunker to mark the anniversary, Myra Collyer, 85, sat behind a typewriter once again and recalled her teenage role as a shorthand typist. The noise down here was far greater with the bombings. Its quietened down a lot. I think I liked it more when it was noisy, she said. Collyer said she thoroughly enjoyed life as an 18-year-old in the hub of the war, earning 75 pence per week. I was shattered when I was posted here because I joined the Womens Auxiliary Air Force to see the pilots, she revealed, adding: I married one in the end. The down side of life in the subterranean command centre was sleeping in the hell-hole known as The Dock. The sub-basement was only 1.2 metres (four feet) high, rat-infested, had no working toilets and stale air. It was horrible, said sprightly 92-year-old Joan Mainprice, who was a secretary to the aides of Cabinet secretary Sir Edward Bridges, the top civil servant. You slept in a nasty little very hard iron bed. There was an enormous great thing which somebody said was a disused sewage pipe. It wasnt a very nice place to be. We used to go out into St Jamess Park at about 6:00 am to get some fresh air. While on an errand, Mainprice once accidentally stumbled into Churchills bunker bedroom which despite the plush desk and comfortable bed, was still a windowless underground brick room. I almost fell on my nose because I walked onto a very deep pile carpet. When I looked up I saw it was Churchills bedroom, so I beat a hasty retreat, she said. Hunter ended up spending an absolutely fascinating two or three weeks working at the Potsdam Conference after the allied Victory in Europe. Meanwhile Mynott had worked the switchboard as the liberation of Europe began. We were ready to take the first calls that were coming in from the beaches on D-Day, she said. When they came through, it was such a fantastic thing to take those first calls. The women went on to live varied, sometimes exciting, sometimes ordinary lives after their time underground. However, their sworn secrecy sometimes meant their close family members died never knowing their hands-on role in crunch wartime decisions. Working around Churchill in his World War II command cell during nightly bombing raids might seem a daunting task, but for the extraordinary ladies of the bunker, they simply got on with their part in seeing off Nazi Germany. No life was normal during the war, said Mynott. And its not British to show a lot of nerves.